May 19 is the deadline to register to vote in the June 3 primary election

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SACRAMENTO, CA - JANUARY 5: An exterior of the state capitol is shown on January 5, 2006 in Sacramento, California. California Governor Arnold Schwarzenegger delivered his state of the state address in the Assembly Chambers of the state capitol today. In his speech, Schwarzenegger admitted to making mistakes with the special election and vowed to work with members of the Assembly and Senate and try to move California ahead in the year to come. (Photo by David Paul Morris/Getty Images)

A new report says California's two major political parties are losing ground as more voters decline to state a party preference.

The Secretary of State's Office said Tuesday that nearly 44 percent of the state's 17.6 million voters registered as Democrats. That's down 1 percentage point from four years ago.

Republicans make up about 29 percent of registered voters, down 2 percentage points.

Voters with no party preference increased slightly, to nearly 21 percent of those registered.

Overall registration is up from 16.9 million voters four years ago.

Since 2010, California adopted a top-two primary system in which candidates from all parties are listed on one ballot. It also now lets voters register online.

May 19 is the deadline to register to vote in the June 3 primary election.